1. Field of the Invention
The present invention relates to an apparatus and method for scanning a frequency in a mobile terminal, and more particularly, to an apparatus and method for scanning a frequency in which a last-used frequency band is periodically re-scanned when a mobile terminal loses a signal and thus scans frequency bands.
2. Description of the Related Art
Recently, portable terminals such as a mobile terminal or a Personal Digital Assistant (PDA) are widely used. Usage of portable terminals is becoming widespread, ranging from simple telephone calls and scheduling to capturing images or videos with a built-in digital camera, watching satellite broadcasts, text editing, playing games, navigating, listening to music, sending short messages, and communicating through multimedia messages capable of transmitting/receiving captured images or videos.
In such a portable terminal, using a certain frequency to transmit/receive signals provides telephone call services and message services. In general, when the portable terminal is turned on, frequency bands are scanned, starting from a frequency band in which a pre-stored frequency exists, and when a signal is lost, as shown in FIG. 1, frequency-scanning is sequentially carried out starting from a last-used frequency band.
FIG. 1 illustrates a scan order of frequency bands when the conventional mobile terminal carries out frequency-scanning. Referring to FIG. 1, a mobile telecommunication system is composed of ten frequency bands. When the mobile terminal loses a service, frequency-scanning is carried out such that a Last-used frequency Band (LB) is first scanned, and thereafter the rest of frequency bands are sequentially scanned.
However, in a case of a mobile terminal using a frequency band with a wide bandwidth for each channel, scanning one frequency band after another is a time consuming process. Examples of such case in which this problem occurs include Wideband Code Division Multiple Access (WCDMA), Orthogonal Frequency Division Multiplexing (OFDM), Wireless Broadcasting (WiBro), and Digital Video Broadcasting (DVB).
In general, operators, who provide the mobile telecommunication systems, each use only a specific bandwidth. When a frequency being used is lost due to an Out-Of-Coverage (OOC) situation or other similar situations, the mobile terminal first scans the LB, and, if no available frequency is detected as a result, the mobile terminal sequentially scans an entire set of frequency bands. However, since each operator uses a different frequency band, scanning of the set entire of frequency bands is equivalent to scanning less usable frequency bands. Accordingly, the wideband mobile telecommunication system may suffer from a significant time delay.